In industry, steam, the vaporized form of water, is often used as a repository of energy due to water's high heat of vaporization. Energy is introduced and extracted by heat transfer, and transported in the form of steam from one area of a manufacturing plant to another through pipes.
Steam trap apparatuses are necessary elements of any steam system because they allow steam to reach its destination in as dry a state as possible to perform its task efficiently and economically. Steam trap apparatuses release condensate, air, and non-condensable gas from a steam space while preventing the loss of steam.
Inadequate steam trapping can lead to various undesirable results from steam system inefficiency to waterhammer, corrosion, leakage, and high maintenance costs.
U.S. Pat. Nos. 4,646,965, 4,830,277, 4,898,022, 5,478,012, 6,220,519, 6,279,593, 6,453,802, 6,571,180, and 6,644,131 disclose apparatus and methodologies which can be used to remove condensate and other unwanted gas from steam systems and which are incorporated by reference herein in their entireties.
The conventional steam trap apparatus is comprised of two actuated valves, piping, and a steam trap which is typically an automatic valve not connected to a control system. One actuated valve is situated upstream from the steam trap while the other is positioned in a bypass line upstream from the first actuated valve. The two actuated valves provide a bypass mechanism which is needed for the cleaning of the steam trap apparatus. The outlet of the steam trap and the bypass valve can lead to a condensate return system which re-heats the condensate to form steam or to a drain.
Steam traps are generally of three types: thermostatic, mechanical, and kinematic; each of which contains a number of specific styles.
Thermostatic steam traps are operated by sensing changes in temperature of a fluid, which by definition can include liquids and gases. Three typical types of thermostatic steam traps are the “liquid expansion traps”, the “bimetallic traps”, and the “balanced pressure thermostatic traps”. Thermostatic steam traps may be a misnomer as these steam traps open and close by mechanical operations. An operating element which is responsive to temperature “changes within the desired range is built into the valve so that when the necessary temperature is reached, they react in a way to block the passage of steam to the outlet.
Mechanical steam traps are operated by sensing changes in fluid density. These steam traps operate by sensing the difference in density between steam and condensate. These steam traps include the “ball float traps” and the “inverted bucket traps”. In a ball float trap, the ball rises in the presence of condensate, opening a valve which passes the denser condensate. In an inverted bucket trap, the inverted bucket floats when steam reaches the trap and rises to shut the valve.
Kinematic steam traps, sometimes called thermodynamic steam traps, are operated by sensing changes in fluid dynamics. These steam traps rely partly on the formation of flash steam from condensate. This group includes the “thermodynamic”, the “disc”, the “impulse” and the “labyrinth” steam traps.
The three types of steam traps are more comprehensively described in industry catalogues from manufacturers such as Spirax Sarco Inc. (Blythewood, S.C.). The Spirax Sarco steam trap catalogue can be found at the following web address: spiraxsarco.com/resources/steam-engineering-tutorials/steam-traps-and-steam-trapping.